These are used for specific code changes relating to each compiler version. There may be no performance impact to choosing a separate classifier in your build. Many of the specific changes relate to use of lambdas and the features introduced in Java 8. Conversant Disruptor was developed prior to that version. There have been some changes around the @Contended annotation over time. However I am no longer using it. So that is not an issue now.
I have been using OpenJDK 11 or above for some time and recommend others to do the same. There have been many improvements to the language and performance features since Java 8 so there is almost no argument to continue supporting it. Of course it is supported in case some users have no choice in the matter. Conversant Disruptor performs well in all versions of Java because it is not using any non-standard language features or backdoors. If you choose the default library with no classifier you should expect excellent performance on the platform of your choice.